In a high speed communication device, a data processor that converts a sampling rate is used (for example, see PTL 1). In a conventional data processor, in the case of converting the sampling rate to n/m times (n and m are integers equal to or larger than 1), first, a filter part performs interpolation by inserting zero data between respective samples of input data and obtains data of n times. Next, a sampling part thins the data from the data of n times to the data of 1/m times.